The overall objective is to study the role of monoclonal cell populations in the origin and subsequent growth of atherosclerotic lesions. Isoenzymes of glucose-6-phosphate dehydrogenase will be used as cellular markers in black females heterozygous for this enzyme and in female hybrid hares which have two separable isoenzymes. Emphasis will be placed on exploration of the selection theory to account for the monoclonality of atherosclerotic lesions. Human studies will include extensive mapping of isoenzyme patterns of intima, fatty streaks and fibrous plaques and determination of magnitude and direction of change in these patterns compared with scars in the skin and with uterine leiomyomas. Studies in the hybrid hare will include dietary manipulations to determine whether changes in isoenzyme patterns of aortic lesions can be produced, and attempts to develop an immunofluorescence method for assessing isoenzyme characteristics in tissue sections.